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# Systems of equations with elimination: potato chips

Sal solves another system of equations using elimination. Created by Sal Khan.

## Want to join the conversation?

• When Sal says to multiple by -2 couldn't you just multiple by positive 2 and subtract instead of add?
• Yes. It is perfectly acceptable to subtract the equations like you said, so long as you subtract on both sides. This would have given you the same solution as well. Nice observation!
• Is Arbegla's name based off of algebra? "Algebra" spelt backwards is "Arbegla".
• Ohhhh
That's why I felt somthing similar from"arbegla" to "algebra"
UPDATE: I search him on google and can't seem to find him
• Sal, how long did it take you to draw these images in your videos?
• How do you solve this equation?
x+y=2
2x+7y=9
• Multiply the first equation by 2, then subtract the second equation. Here:
2x+2y=4
-(2x+7y=9)
0x-5y=-5
-5y=-5
y=1
Now, just plug 1 back into either equation to solve for x.
• People in this kingdom are fat five cupcakes
3 potato chips bags
• The parties could be flawed, possibly because each man/woman could have eaten less because Arbegla may have ordered less than needed? Or are they assuming that it is one of those times where he ordered enough/more than enough?
• You are quite right eshi21 however this is a scenario so just ignore it.
(1 vote)
• haha get it? Arbegla? Algebra? GET IT?!?!
• yes it is funny
• When sal manipulates the second equation by multiplying it with negative 2. Can we instead subtract -700w. because technically that would all manipulate the equation, but in a different way and then also we will be able to cancel out w in the equation.
• That doesn't seem like it would quite work. The only way you could subtract 700w would be if you had already added the two equations together, and then you would still end up just moving w to the right-hand side of the equation:
300m+700w=2300.
Subtract 700w from both sides:
300m=2300-700w.
The way Mr. Khan does it in the video maintains the same relationship between the equation, and also gives us the ability to cancel out one of the variables. Hopefully that helped, and if it didn't you can tell me.
• i dont understand when in the end of the problems we have -1000 -500 and it gives us 2, the same with 300 - 100 = 3

Thank you.
• It doesn't have: -1000 -500 = 2 OR 300 - 100 = 3
You are ignoring the division
The video has: -1000 / (-500) in fraction form. The bar in the middle of the fraction is division. When you divide, it = 2
the video also has: 300 / 100 in fraction form. Again, this is division, not subtraction.
When you divide, it = 3

Hope this helps.
• how did you get 1200 for 300w and 200m ?? wouldn't it be 500
and also how did u get 1100 for 100 and 400?? wouldn't it be 600